Apparatus for constructing screening elements



Nov. 2, 1954 A c, D. COULTER APPARATUS FOR CONSTRUCTING SCREENING ELEMENTS 5 Sheets-Sheet 1 Filed Sept. 19. 1950 INVENTOR.' mam.

Nov. 2, 1954 c. 0. COULTER APPARATUS FOR CONSTRUCTING SCREENING ELEMENTS 3 Sheets-Sheet 2 Filed Sept. 19, 1950 I INVENTOR.

macaw BY ATTORNEYS.

Nov. 2, 1954 c, cou -r R 2,693,205

APPARATUS FOR CONSTRUCTING SCREENING ELEMENTS Filed Sept. 19, 1950 3 Sheets-Sheet 3 l fit, %g6

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United States PatentO APPARATUS FOR CONSTRUCTING SCREENING ELEMENTS Clarence D. Coulter, Los Angeles, Calif assignor to Southwestern Engineering Company, Los Angeles, Calif., a corporation of California Application September 19, 1950,. Serial No. 185,583 Claims. (Cl. 140-109) This invention relates to the construction of screening elements'which comprise a screen cloth member of extended area. held taut in a marginal frame. The screen cloth member of such a screening element may comprise a pervious. mesh sheet of suitable material .such as metal, plastic material, or fibrous threads, the

her 10, 1949, in which such screening elements are mounted by clamping between superimposed frame members.

The principal object of this invention is to provide an advantageous apparatus for constructing such a screening element, with the screen cloth tensioned uniformly in all lateral directions and securely held in this laterally tensioned condit'on by a marginal mounting frame secured to the screen cloth adjacent the periphery thereof. The lateral tensioning of the screen cloth is sufficient to draw it uniformly taut in all directions so as to remove all wrinkles or slack, and is preferably suflicient to actually stretch the cloth somewhat to facilitate making it drum tight when assembled in a screening apparatus such as that shown inthe above mentioned Miller et al. application.

A further object is to provide an; apparatus for constructing such ascreening element in which the screen cloth member may be cut from a rectangular piece of screen cloth whose dimensions may be but little greater than those of the screen-cloth member in the finished screening element, so as to avoid excessive waste of screen cloth.

A particular object is to provide an advantageous 'work support structure for use in a'fastening operation to secure a taut screen cloth member to a, marginal mounting frame.

- A further object is to" provide an advantageous combination of a tensioning device for receiving and drawing taut a rectangular piece of screen cloth, and a work support structure for supporting the tensioning device and screen cloth during attachment of the screen cloth toa marginal mounting frame while the cloth is held taut by the tensioning device.

In'th'e-apparatus of the present invention, a rectangular piece of screen cloth is mounted in a tensioning device adapted to clamp the clothtightly along each lateral edge thereof, and outward tension is applied along substantially the entire length of each lateral edge of the cloth so as to draw it. taut. in all. directions. The screen ,clothis supported between upper and lower members of a marginal mounting frame located inwardly from the lateral edges of the cloth, and the mounting frame. members are secured to the cloth by fastening attachment thereto atv a plurality of angularly spaced positions while keeping the screen cloth taut by continued outward tension applied along substantially the entire length of each lateral edge, outside the location of the mounting frame members. The invention includes a suitable support structure adapted to support the tensiouing device and the screen cloth together with its 2,693,205 Patented Nov. 2, 1954 mounting frame members, for convenient manipulation during attachment of the mounting frame members to the screen cloth.

The invention may be described more fully by reference to the accompanying drawings illustrating a preferred form of apparatus in accordance with this invention, in which:

Fig- 1 is a plan view of. a screen tensioning device, showing a rectangular piece of screen cloth mounted therein;

Fig. 2 is a vertical section on line 22 in Fig. 1 but on alarger scale;

Fig. 3 isa plan view of the tensioning device and screen cloth, together witha marginal mounting frame for the screen cloth, mounted on a support structure for use in attachment of the cloth to the mounting frame, with the screen cloth and its mounting frame partly broken away;

Fig. 4 is a plan viewof-a portion of the support structure and tensioning device on a larger scale than Fig. 3, with the tensioning device partly broken away and with a fragmentary partial showing of a screen cloth and its mounting frame;

Fig. 5 is a vertical section on line 5-5 in Fig. 4, on a still larger scale;

Fig. 6 is a partial side elevation of the support structure shown in Fig. 3, partly insection;

Fig. 7 is a fragmentary plan view of a marginal portion of a completed screening element, with certain parts broken away; and

Fig. 8 is a vertical sectional view showing a portion of a completed screening element mounted in a screentioned Miller et a1. application.

The tensioning device indicated generally at A in Figs; 1 and 3 comprises a rectangular support frame 10 made of four side members 11 each in the form of a length of channel iron having a bottom web 11a and two upstanding side flanges 11b, welded or otherwise rigidly secured together at the corners of the frame, and four separate clamping devices 12 adjustably mounted on the respective side members 11. Each clamping device 12 comprises a lower clamping bar 13 supported on the corresponding frame side member 11 for lateral sliding movement, as by means of a plurality of support and guide pins 14 secured to the side flanges 11b of member 11 and slidably engaging correspondingly spaced bores 15 (Fig. 5) in the clamping. bar 13. Each clamping device further includes an upper clamping bar 16 adjustably supported-on the lowerbar 13 by a plurality of vertical clamping bolts 17 extending through holes 18 in the upper bar and engaging. threaded bores 19 in the lower bar. The upper and lower faces of the clamping bars 13 and 16 respectively are adapted for clamping engagement with an edge portion of a rectangular piece of screen cloth. The lower bar 13 hasa flat horizontal upper face 13a for supporting. engagement with the screen cloth. The lower face vof theupper bar is shown as recessed and sloping upward at a slight. angle, from its inner edge to a position adjacent its outer edge, as indicated at 16a; to insure positive gripping of the screen cloth at the inner edges of the twoclamping bars.

The tensioning device is also provided with means for exerting an outward lateral force against each of the clamping devices, such means being shown as comprising a plurality of jack screws 21 seated in threaded bores 22 (Fig. 2) in each lower clamping bar 13 and extending through openings 23 in the outer flange 11b of each channel member 11 and provided with an adjusting nut 24 bearing againstthe outer face of said flange. By uniformly tightening the adjusting nuts 24 on all the jack screws of any clamping device 12, that clamping device and the margin of. the screen clamped therein may be moved forcibly outward to tension the screen. The. bars 13 and 16 of each clamping device extend substantially the entire length of the corresponding frame side member 11 so. that the resulting outward tension may be applied alongsubstantially the entire length of each lateral edge of a rectangular piece of screen cloth.

In order to permit a marginal mounting frame to be secured tothe rectangular piece of screen cloth .as near as mg apparatus'of the type described in'the above menpossible to each lateral edge thereof and inside the tensioning device A, with a flange on the lower member of the mounting frame projecting outwardly beyond the edge of the screen cloth in the finished screening element, the lower portion of the inner face of each lower clamping bar 13 is shown as recessed outwardly as indicated at 26. For use in constructing screening elements of circular shape, each of the side members 11 of the support frame may advantageously be cut away or recessed outwardly from its inner edge adjacent the midlength thereof, as by cutting out the middle portion of the inner edge along a line forming an arc of a circle about the center of the support frame, as indicated at 27 (Figs. 1, 3, 4 and 5). This permits the clamp bars 13 and side members 11 of the tensioning device to be located as close as possible to a circular mounting frame so that a rectangular piece of screen cloth of the smallest possible size may be used to construct a circular screening element of a given diameter, thereby minimizing the waste of screen cloth.

The apparatus also includes a support structure indicated generally at B in Figs. 36, comprising a table member 30 having a flat horizontal upper surface 30a, rotatably supported on a central upstanding post 31 for rotation to any desiredangular position about a central vertical axis. The rotatable supporting table 3%} conforms substantially to the shape of the marginal mounting frame of the screening element. I have illustrated a form of apparatus adapted particularly for use in con structing circular screening elements having an annular marginal mounting frame, and the table 30 is accordingly shown as a horizontally disposed disc, whose diameter is somewhat less than the spacing between each pair of opposing side members 11 of the tensioning device, as shown particularly in Fig. 3, so as to provide spaces between the periphery of the disc 30 and the side members for receiving a mounting frame for the screen cloth as described hereinafter. The table member 30 is shown as provided with a shallow annular groove or recess 32 at the periphery of its upper face, for a purpose to be described later.

A plurality of angularly spaced pins 33 are mounted in support blocks 34 secured to the underside of table member 30 and project outwardly beyond the peri hery of the table member and below the upper face thereof for su porting the tensioning device A as shown particularly in Figs. 3, 4 and 5. Thepins 33 are preferably arranged in angularly spaced pairs or groups, the pins of each pair or group being spaced relativelv close to- ,gether as indicated for exam le at 330: and 33b in Fig. 3. In the present construction I have shown four such pairs of closely spaced pins, these pairs being equally spaced from each other around the eriphery of the t ble member 30. The pins 33 are rem vablv mounted. as bv extending s idably through bores 35 in the blocks 34 so that any of these pins mav be removed and reinserted during operation, as des ribed hereinafter.

The table member 30 is also provided with another pluralitv of angularly s aced pins 36 mounted thereon and proiecting outward beyond the peri hery thereof and below the upper face of the table member but above the pins 33, for supporting a mar inal mounting frame for the screen cloth around the peripherv of member 30 and inside the rectan ular tensioning device A. I have shown four of these pins 36 spaced approximately 90 apart around the eriphery of the table member. and said ins are preferab v su ported s idably in radial bores 37 in the disc so that they may be removed and reinserted if desired. The pins 3 for supporting the tensionin device project outward sufiiciently to extend beneath the side members 11 of the frame 10. The pins 36 project outward a shorter distance than the pins 33 so that their outer ends are spaced inward from the side members 11 of the tensioning device when said pins are located adjacent the mid-lengths of said side members as indicated in Figs. 3, 4 and 5.

The above described apparatus is adapted particularly for the construction of screening elements comprising a circular sheet of screen cloth C (Figs. 7 and 8) and a circular marginal mounting frame indicated generally at D, having lower and upper members secured to the marginal portions of the lower and upper faces of the screen cloth. When the screen cloth and its marginal mounting frame are of metal, the mounting frame members are preferably secured to the screen cloth by welding attach ment at suitable intervals around the periphery. Referring particularly to Figs. 3, 5 and 7, the lower member of the marginal mounting frame D of the screen element may comprise a rigid metal member such as ring 33 having a fiat upper face 33a and an outwardly projecting annular mounting flange 39 at its lower edge. The upper mounting frame member may comprise a fiat metal member such as ring 41 of approximately the same radial dimensions as the upper face 38a of member 33. The mounting frame for the screen preferably also includes a pair of cushioning rings or members 42 and 43 of rubber or other resilient material interposed between the screen cloth and the lower and upper frame members 38 and 41 to provide a resilient cushioned mounting for the screen cloth at the inner edge of the marginal mounting frame D. The resilient members 42 and 43 are preferably cemented or otherwise secured to the metal frame members 38 and 41 respectively.

In constructing a screening element with the above described apparatus, a rectangular piece of screen cloth indicated at C is mounted in the tensioning device A and is drawn taut by applying outward tension thereon along substantially the entire length of each lateral edge. These operations are preferably, but not necessarily, carried out while the tensioning device A is mounted on the support structure B. According to this preferred procedure, the lower mounting frame member 38 and the lower resilient cushioning member 42 of the screen mounting frame D are first mounted on the support structure B, with the member 38 resting on the short upper pins 36 and the inner margin of the resilient member 42 received in the peripheral groove 32 of table member 30, as shown in Figs. 3 and 5. The frame member 38 is centered around the table member 30, and the groove 32 serves to properly position the resilient member 42 on said member 38 in centered relation thereto and with the upper face of the resilient cushioning member substantially flush with the top of the table member 30.

Thetensioning device A is then mounted on the support structure B, with the upper clamping bars 16 and bolts 17 removed, the tensioning device A being centered about the support structure B and being mounted with the middle portion of each side member 11 supported upon one of the pairs of pins 33, as shown in Fig. 3. It will be seen from Figs. 3, 4 and 5 that the arcuate notches or recesses 27 at the inner faces of side members 11 of the tensioning devicepermit these side members to be lowered past the annular flange 39 of the screen mounting frame D to the position shown, so as to rest on the radially projecting pins 33, and that the recesses 26 in the lower clamping bars 13 permit these bars to clear theflange 39 when the tensioning device is thus mounted on the support structure.

A rectangular piece of screen cloth C is then placed on the support structure B over the members 38 and 42 and on the lower clamping bars 13 of the tensioning device, with the lateral edges of the screen cloth projecting beyond the lower member 38 of the screen mounting frame and overlying the inner portions of the lower clamping bar 13. The part of the screen cloth within the members 38 and 42 rests upon the upper surface 30a of table member 30 and is supported thereby in a substantially flat position.

The upper clamping bars 16 are then mounted over the screen cloth, the clamping bolts 17 being screwed into the lower clamping bars 13 beyond the lateral edges of thescreen cloth as indicated in Fig. 2. It will be seen that the dimensions of the rectangular piece of screen cloth C are such as to permit its lateral edge portions to be received between the inner portions of clamp bars 13 and 16, but to lie within the limits defined by the bolts 17. The dimensions of the piece of screen cloth used are therefore but little greater than the external diameter of the portions of the mounting frame D adjacent the screen cloth, which is the diameter to which the screen cloth is trimmed in the finished screening element.

The screen cloth is then clamped and tensioned by the tensioning device. To insure the screen cloth being uniformly taut in all directions, without wrinkles or slacktherein, the preferred procedure is to first tighten the clamping bolts 17 at one pair of opposing sides of the tensioning device A so as to clamp the corresponding opposite edges of the screen cloth in that pair of clamping devices 12, and then turn the nuts 24 on the jack screws 21 for these two clamping devices so as to exert outward pressure on the clamping devices 12 and cloth in the.correspondingclamping devices 12,- and the bolts 17 at the first pair of lateral edges are loosened.

-The jack screws. 21.at the .secondpair of edges are then operated to tensionthe. screen cloth in the otherdirection while the first pair of edges are free fromtclampmg engagement by their. respective clamping devices. The clamping bolts 17 at. the firstpair of opposite edges are then again tightcnedto reclamp those edges in theclamp- .ing devices,- and the corresponding jack screws are operated so as to again. tensionthe screen in thezoriginal direction and remove any remaining wrinkles or slack in the screen. These operations result in the screen cloth being clamped and subjected to lateral outward tension along substantially the entire length of each lateral edge thereof, so that it is held taut in all directions. The outward tension applied is preferably sufficient to not only make the screen uniformly taut 1n all directions, but to actually stretch the cloth somewhat.

The upper cushioning member 43 and upper mounting frame member 41 of the screen mounting frame D are then placed in position on the screen cloth C in alinement with the lower members 42 and 38 respectively, as shown in Figs. 3 and 5, and the lower and upper mounting frame members 38 and 41 are secured to the screen cloth C, preferably by welding when the mounting frame and screen cloth are of metal. For this purpose I may use any suitable type of spot welding machine located at one side of the support structure B and provided with an upper electrode 45 adapted to be brought into engagement with the upper frame member 41 and a lower electrode 46 adapted to be brought into engagement with the lower face of the lower frame member 38, as illustrated in dot-dash lines in Figs. 4 and 5. These electrodes may be mounted on the welding machine in any suitable manner for movement into and out of these positions, the lower electrode 46 being shown as carried by arm 47 adapted to extend beneath the side members 11 of the tensioning device A when the table member 30 of support structure B is rotated to any desired angular position about its axis, and said electrode 46 being adapted to extend upward between the outer periphery of the table member 30 and the adjacent side member 11.

It will be evident that by rotating the table member 30 on the central post 31, together with the tensioning device A, screen cloth C, and marginal frame D carried thereon, any desired points on the mounting frame members 38 and 41 may be brought into position between the electrodes 45 and 46, for spot welding, and that pins 33 and 36 may be quickly removed when necessary to avoid conflict with the electrodes if the electrodes remain in or close to their operating positions during such rotation. If one of the pins 33 of a closely spaced pair, such as pin 33a in Fig. 3, is removed, the other pin of that pair, such as pin 33b, will serve to support that side of the tensioning device A. Since the lower member 38 of marginal frame D is held between the tensioned screen cloth C and the pins 36, any one of these pins may be removed after spot welding adjacent that pin, without causing displacement of said member 38 from its proper position.

The table member 30 and assembled parts carried thereby are preferably first turned to a position in which all the pins 33 and 36 are clear of the welding electrodes and the mounting frame members 38 and 41 spot welded to the taut screen cloth C at one point adjacent one of the pins, as illustrated by the position of the electrodes in Fig. 4, and are then rotated through successive 90 movements and the frame members and screen cloth spot-welded at additional points 90 apart. The assembly is then rotated successively to other positions for spot welding midway between the first series of welds, and this is repeated to make additional series of welds each midway between previous welds, until the frame members 38 and 41 are spot-welded to the screen cloth at sufficiently close intervals around their entire circumference as indicated, for example, in dotdash lines at 48 in Fig. 7. In order to spot weld at a position normally occupied by any one of the pins 33, that pin may be removed, and may be reinserted after making that weld. After welding adjacent any one of the pins 36, that pin may'be removed and leftout; while making the remaining spotwelds.

'When the attachment. of the screen cloth= C" to"- the mounting frame D is completed, thetensioningdevic'e A may be removed from the. support structure B, together with the screen cloth clamped therein and the marginal mounting frame secured to the screen cloth. The screen cloth within. the marginal frame D is now held taut by its attachment to said frame. The portions of the screen. cloth projecting beyond the frame D may then be trimmed off flush with the outer periphery of the. upper frame member 41, a's indicated at 50in Fig. 7,. completingthe construction of the screening element and leaving the remainingtaut screen cloth member C tightly secured to the marginal frame' D. The finished screening element may then be removed through the bottom of the frame 10 of tensioning device A. The bolts 17 and upper clamping bars 16 may then be removed, to permit removal of the trimmed off outer portion of the original rectangular piece of screen cloth.

The completed screening element of the particular form shown is adapted particularly for use in screening apparatus of the type shown in the above mentioned Miller et al. application, and the projecting horizontal flange 39 of the lower frame member 38 provides an advantageous means for mounting the screening element in such apparatus. Such an application thereof is illustrated in Fig. 8, in which the flange 33 is clamped between flanges 51 on two superimposed cylindrical spacer frames 52 by means of a clamp ring 53. By providing the flange 39 at a level somewhat below the circular screen cloth member C, the screen cloth is thus locatedat or closely adjacent the lower edge of a discharge port 54 in the upper spacer member 52 so as to permit free outflow of oversize material from the screen through said discharge port. When the screening element is so mounted, the screen clothmay be further tensioned so as to make it drum tight by applying a force directed downwardly against the screen along the vertical axis thereof, as indicated by the arrow at 55 and as described fully in said Miller et al. application.

I claim:

1. In apparatus for constructing a screening element, the combination comprising: a screen tensioning device having four side members forming a rigid rectangular frame; a support structure having a table member extending horizontally and mounted for rotation about a vertical axis; a plurality of angularly spaced members mounted on said table member and projecting outwardly therefrom below the top of the table member to positions for supporting engagement with the side members of the tensioning device; means mounted on the table member and projecting outwardly therefrom to support a mounting frame member; a separate clamping device slidably supported on each of said side members of the tensioning device for outward movement thereon and each adapted to receive and clamp a lateral edge of a rectangular piece of screen cloth, said clamping devices being so located as to support the screen cloth over the table member and over the position at which the mounting frame member is supported; and means engaging the respective clamping devices and side members for forcibly moving the clamping devices outward to tension the screen cloth.

2. In apparatus for constructing a screening element, the combination set forth in claim 1, in which said table member is circular and each of said side members of the tensioning device is recessed outwardly from its inner edge for a limited portion of the length midway between the ends thereof.

3. In apparatus for constructing a screening element, the combination set forth in claim 1, in which each of said clamping devices comprises upper and lower clamping bars extending substantially the entire length of the corresponding side member of the tensioning device and adapted to receive and clamp a lateral edge of the screen cloth therebetween.

4. In apparatus for constructing a screening element, the combination as set forth in claim 3, in which the lower portion of each of the lower clamping bars is recessed outwardly from its inner edge.

5. In apparatus for constructing a screening element, a support structure comprising; a horizontally extending table member; means rotatably supporting said table member for rotation about a vertical axis; a plurality of angularly spaced pins mounted on said table member and projecting outwardly therefrom below the top of the table member at four positions substantially equally spaced around the periphery of the table members to support a rectangular screen tensioning device; and another plurality of angularly spaced pins mounted on said table member and projecting outwardly therefrom below the top of the table member to support a frame memher, said last mentioned pins being above and projecting a shorter distance than the first-mentioned pins; said table member being provided with a shallow recess at the periphery of its upper face, to receive and position a thin member mounted upon and projecting inwardly from a frame member supported on said last mentioned pins.

References Cited in the file of this patent Number UNITED STATES PATENTS 

